In recent years, the increasingly smaller size and greater thinness of mobile phones and other information terminals have led to numerous products with display parts and other moving parts made to slide or turn with respect to keyboard parts and other fixed parts for the purpose of improving the portability, operability, and ease of viewing of the displays. In such information terminals, two housings which change in position relative to each other, for example, a display side housing and a keyboard side housing, are required to be able to be easily made to slide or turn. To enable the slide movement or turning movement operation to be easily performed, it is desirable that there be an assist force in a direction causing approach to the movement end position near the two ends of movement of the two housings.
As a system which gives such an assist force, an assist spring mechanism which assists opening and closing of a slide type mobile phone is disclosed in Japanese Laid Open Patent Publication No. 2008-501288A. The assist spring mechanism which is disclosed in Japanese Laid Open Patent Publication No. 2008-501288A attaches a compression spring with two ends which have a degree of freedom of rotation at the fixed side and the moving side to the housings, makes the housings open and close along a slide guide, and, at that time, makes the compression spring compress and simultaneously makes it turn to cause an assist force to act (see FIG. 1).
Further, a mechanism which makes a moving member move between a pulled-in position and a pulled-out position with respect to a base member wherein the moving member is made to slide from an intermediate position of movement by the biasing force of a spring automatically to either the pulled-in position or the pulled-out position is disclosed in Japanese Laid Open Patent Publication No. 2006-26332A. The base member and moving member which Japanese Laid Open Patent Publication No. 2006-26332A covers are the main body of storage furniture etc. and a drawer which is pulled out from the main body. A slide assist system is provided between the main body and the drawer.
However, the assist spring mechanism which is disclosed in Japanese Laid Open Patent Publication No. 2008-501288A does not allow other parts to be arranged in the housing in the range in which the compression spring turns. Wasteful space is formed in the housings making further reduction of thickness and size difficult. Further, in Japanese Laid Open Patent Publication No. 2006-26332A, the moving member is made to move linearly with respect to the base member without making it turn, but the structure is complicated and there are limits to reduction of size. The system was not suited to mobile phones and other small sized devices.